Plant roots and practical value of plant root symbionts

Transcription

1 Plant roots and practical value of plant root symbionts Conference at Aleksandro Stulginskio University, Akademija 2 May 2016 Plant Roots: Biology, Morphology, and Functions Priv. Doz. Dr. habil Ewald Sieverding University of Hohenheim Institut for Plant Production and Agroecology in the Tropics and Subtropics Garbenstraße 13, Stuttgart-Hohenheim,Germany D Sankt Johann, Auf dem Ewiger 15, Germany sieverdinge@aol.com

2 What do plant roots do Fix plants to soil Absorb water and nutrients from soil Transport water and nutrients to upper parts Store assimilates of upper parts (which are remobilized at certain times, or are harvested) Exudate components to soil for mineralisation of nutrients Act as hosts for symbionts (Rhizobia & Mycorrhiza) and on surface for associations with bacteria and fungi

3 Roots of different plant species can have very different morphologies Different root morphologies 1) Aufrechter Ziest; stiff hedgenettle (Stachys recta) 2) Frühes Hungerblümchen; nailwort (Erophila verna) 3) Feld-Beifuß; field mugwort (Artemisia campestris)

4 Roots fix plants in soils (cereals) importance of fine roots Source: BASF Deeper and more roots, and less shoot development give more robust crop

5 Roots of crops grow shallow or deep Peas Pisum sativum Phacelia sp. Buck wheat Fagopyrum sp. Vetches Vicia spp. sunflower Helianthus annuus

6 How deep do agronomic plants grow

7 Where is most root biomass Rhaphanus sativus Phacelia Lupinus luteus

8 Mixed crops can better explore soil for nutrients and water Mixtures are favoured for intercrops (green manure / greening)

9 Functional components of roots of some crops

10 What influences root development? There is are some relationships between availability of nutrients and root development (well known, nothing new) -The lower the nutrient availability, the better the root formation & vice versa -Phosphate improves root development (- and formation of flowers) -Light, temperature and water -Airation of soil (compactation)

11 Phosphate is important for early root development Root development at different P availability (maize)

12 More light more roots

13 Influence of temperature Plant species may differ in temperature requirements Indirect effects possible: degree C max. Activity of microbes, Mineralization; N availability

14 Microorganisms in rhizosphere (living on root exudates)

15 Plant Root Symbionts: - Rhizobia for N2 fixation - Mycorrhiza (for nutrient uptake and transport) 15

16 Legumes form symbiosis with Rhizobium in roots and fix air nitrogen

17 Genetic Resources of Rhizosphere Microorganism 17

18 Non-inoculated inoculated Source: Presentation given by H.M. Fischer. Microbiological Institute, ETH, Zürich, Switzerland, 10 Jan Genetic Resources of Rhizosphere 18 Microorganism

19 Genetic Resources of Rhizosphere 19 Source: Presentation given by H.M. Fischer. Microbiological Microorganism Institute, ETH, Zürich, Switzerland, 10 Jan. 2013

20 Rhizobia efficacy is strain dependent Rhizobium strain Total N (mg plant -1 ) N8 3.7 N5 3.4 S6 3.0 S C

21 Rhizobia inoculants Legumes seed-inoculation technology Liquid inoculants Peat based inoculants Pellet Granular peat based inoculum Commercial products 21

22 Genetic Resources of Rhizosphere Microorganism 22

23 Soya grain yield after inoculation with Rhizobium & fertilizing with N Kg/ha relativ % N in seed protein

24 Practical value of Rhizobium- Legume symbiosis Effective legume-rhizobium symbiosis can fix kg / ha nitrogen (from air); corresponds to ca kg Urea Fixed N 2 is used for own legume production. Surplus of N 2 for follow crop N 2 accumulation of kg/ha for rotation crop possible Legume-Rhizobium symbiosis is sensitive to mineral nitrogen fertilization at planting; it is not recommended to add any Nitrogen when inoculating with Rhizobium Effective symbiosis needs phosphate (in fertile soils P is biologically provided by arbuscular mycorrhiza) & special micro-nutrients (Mo, Co, Fe)

25 Plant Root Symbionts: - Rhizobia for N2 fixation - Mycorrhiza (for nutrient uptake and transport) 25

26 Mycorrhizas mutualistic symbioses 26

27 Ectomycorrhizal fungi (about 5000): Most are Basidiomycetes; also some Ascomycetes (truffles); Zygomycetes (ectendo = Endogone) Lactarius (left) and Boletus (right) About 2000 plant species form ectomycorrhiza, mainly trees: Pinaceae, Cupressaceae, Fagaceae, Betulaceae, Salicaceae, Dipterocarpoideae, Myrtaceae, also Eucalyptus species - All are of obligate mycotrophic character Genetic Resources of Rhizosphere Microorganism 27

28 Ectomycorhhizal inoculum applied in nursery, or at time of transplant Genetic Resources of Rhizosphere Microorganism 28

29 Arbuscular Mycorrhiza =endomyorrhiza Fungi belong to Glomeromycota Multinucleous organisms Formed by >70 % of plant species of plant kingdom with about 300 fungal species of the Glomeromycota. Important crops like all cereals & grasses, potatoes, vegetables, flowers, fruit trees form mycorrhiza. Some crops never form mycorrhiza: rape, sugarbeet, brassicas Some need special mycorrhiza: blue berries, Ericaceae, orquideae 29

30 Root external mycorrhizal mycelium: increase of exploited soil volume times higher than by roots alone Genetic Resources of Rhizosphere Microorganism 30

31 Mycorrhiza absorbs Plant available phosphate More efficient than the root NM M NM M Phaseolus vulgaris Not fertilized with P Fertilized with 100 kg P /ha Phosphat is a growth limiting element in soils, and is mainly needed at the beginning of season Dependency of plants on mycorrhiza: Some are obligate Some are facultative Root Morphology dependent Onion bulbs grown in soilless mixture (peat/vermiculite/perlite) and treated (A) or not (B) treated with BACTOLiVE AM BASIC inoculum (after 3 weeks of inoculation

32 Other Nutrients Macro nutrients: direct uptake and transport by hyphae: P, NO - 3, NH + 4, Ca, Mg, (K? - via mass flow?) Micro nutrients: direct uptake & transport by hyphae: Zn, Cu, S, B, Mo (essential nutrient) Cd, Ni, Sr, Se (heavy metal) Br, J (not essential elements) Indirect? (Higher concentrations in mycorrhizal plants): Genetic Resources of Rhizosphere Microorganism Fe, Mn, Cl (assumed also Na, Co, Si) 32

33 Other benefits of Arbuscular Mycorrhiza (AM) Plant water relations Plant health (bio control of root pathogens and more resistant to nematodes) Interaction with soil microorganisms AM improve biological N2 fixation by Rhizobia AM improve plant growth promoting bacteria and P solubilizers 33

34 Nematode control in vegetables by arbuscular mycorrhiza

35 GLOMALIN Very important part of SOIL FERTILITY Glomalin glues soil particles together and forms stable soil aggregates Potentially the most important benefit of mycorrhizal fungi for a sustainable agricultural production

36 Water stable aggregates (by Glomalin) Grasses and legume are heavy mycorrhizal excellent soil aggregation Sugar beet doesnot form mycorrhiza no soil aggregation

37 Water stable aggregates

38 Practical value of arbuscular mycorrhiza Savings of 50% Phosphate fertilizer, if mycorrhiza is promoted Making more effective use of fertilized P Making use of low soluble P-fertilizers (rock phosphates) More balanced uptake of fertilizer nutrients (N, K, Mg, micronutrients)= with better plant growth Better survival of plants during short drought periods Significant better N-fixation by legumes via Rhizobium Plays role in soil health (nematode control) and in soil aggregation (soil fertility)

39 Summary Without roots no shoots = without roots no yield Early root development depends (in general) on availability of phosphate; it is well known that too much nitrogen overproportionally favours shoot development Optimum root development at the start of the vegetation is important for yield (nutrient use efficacy, water use efficacy) It appears that a lot of research is still required what roots concern, and what their symbionts concern more needs to be done to make optimum use of the natural resource root in agricultural production (it appears that more emphasis is placed on fertilizing the above ground part of crops root research means: a lot of dirty work) Roots are generally living in association with surrounding microorganisms, or in symbiosis with them without microorganisms there is no plant nutrition & likely low yields.

40 THANK YOU VERY MUCH